1. Field of the Invention
The invention relates in general to a manufacturing process of a semiconductor device, and more particularly to a manufacturing process of a vertical type solid state light emitting device.
2. Description of the Related Art
Light emitting diode (LED) emits a light by converting electric energy into photo energy. Conventional vertical type LED includes an epitaxy growth layer and an upper electrode layer and a lower electrode layer respectively disposed on a top surface and a bottom surface of the epitaxy growth layer. When electricity is provided to the upper and the lower electrode layer of the LED, the current flows through the epitaxy stacking structure, which releases energy in the form of a light when electrons and electron holes are combined.
In the manufacturing process of the vertical type light emitting diode, a light emitting stacking structure is formed on a sapphire substrate whose lattice constant is close to that of the epitaxy growth layer, wherein the epitaxy can easily grow on the sapphire substrate. Next, a conductive substrate is disposed on a top surface of the light emitting stacking structure. Then, the sapphire substrate is removed from a bottom side of the light emitting stacking structure by mechanical grinding process or laser lift-off process. Then, a lower electrode layer is formed on the bottom side of the light emitting stacking structure to complete a conventional vertical type light emitting diode.
However, there are problems arising from the conventional mechanical grinding technology used for processing the sapphire substrate. That is, the grinding thickness is hard to control at precision and the process is time consuming. Although the laser lift-off technology can quickly lift off the sapphire substrate, the laser lift-off equipment is expensive. Moreover, the adjustment of laser power is crucial to the yield of the manufacturing process. If the laser power is too high, the epitaxy growth layer will be damaged; conversely, if the laser power is too low, the sapphire substrate cannot be removed smoothly. In short, the technology of adjusting laser power is complicated, and is not a reliable technology in the manufacturing process.